I was also on 50mg Zoloft and just felt 'flat' and continued having some intrusive thoughts and constant checking if stove was off before leaving home, etc ..i got tired of the 'flatness', numbness, having no emotion..also felt the same 'flatness' after being on other SSRIs for awhile..so I asked the DR if there were any alternative meds I could try..he suggested 18mg/day of Inositol..it's helped a bit and now in addition i'm trying 900mg of St. John's wort..i should feel the effects in about 2 more weeks and i'll let you know..might also add 50-100mg of 5-htp and see if that helps..